Question: Simplify the following expression and state the condition under which the simplification is valid. $a = \dfrac{t^2 - 64}{t - 8}$
Answer: First factor the polynomial in the numerator. The numerator is in the form ${a^2} - {b^2}$ , which is a difference of two squares so we can factor it as $({a} + {b})({a} - {b})$ $ a = t$ $ b = \sqrt{64} = -8$ So we can rewrite the expression as: $a = \dfrac{({t} {-8})({t} + {8})} {t - 8} $ We can divide the numerator and denominator by $(t - 8)$ on condition that $t \neq 8$ Therefore $a = t + 8; t \neq 8$